Method for making acid reagents



Sep@ 37 E946., F. c. FAHNESTOCK Erm. 407,22

METHOD FOR MAKING ACID REAGENTS Filed Dec. 14, 1943 Patented Sept. l?,i946 ZZSZ sono associare Frank C. Fahnestock, Haddoniield, N. Il., andWilliam A. Hagerbaumer, Haverford Township, Delaware County, Pa.,assignors to Socony- Vacuum @il Company, incorporated, a corporation oiNew York -application December le, i943, Serial No. 514,222

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This invention has to do with the making of various acid reagentsutilizing the oxides or sul- -un For example, in sulfonation processes,it is frequently desired to use solutions of sulfur trioxide in liquidsulfur dioxide, or oleum of quite high concentration A This inventionlis directed to a convenient and highly efficient method for handling thepreparation of many such reagents.

The invention may be understood by reference to the attached drawing,the single figure of which shows, in. diagram form, apparatusappropriate to carrying out the invention, which may be operated asfollows:

Turning to the drawing, i is a stripper tower. having a fractionatingsection 2 and an exhausting section 3. An oleum, say one containing 20S03 is fed to this tower through pipe t, passing through heater 5 andentering the tower through spray 6. The function of this tower is tostrip S03 from the oleum, and to this end there is introduced, by pipe land spray 8, a stream of vaporous sulfur dioxide. This stream of gas maybe heated in heater 28. Control of tower conditions is eil'ected in theusual manner by a wet reilux of liquid sulfur dioxide, introduced frompipe s through spray i0. Additional heat, as necessary, may be suppliedby reboiler il. Operating in this fashion, an oleum may be strippedreadily to a W concentration, say for example to one containing 3% S03,which denuded oleum may be removed from tower l through pump l2 and pipei3, under the control of liquid level valve i6. The overhead product ofstripping tower l, departing through pipe l5, consists oi' a gaseousmixture of SO2 and S03.

Instead `of the fractionator type of equipment shown, other types ofstripper may be used, as, for example, a film type of evaporator.

This mixture ls introduced into absorber tower l, below its packing Il,through spray I 8, having rst been cooled by passing through cooler 2S.Liquid SO2 is introduced at the top of tower l@ from pipe i9, throughspray 20, in amounts which may be controlled by liquid level controlvalve 2i, or otherwise, if desired. There is collected in the bottom oftower l5 a liquid SO2 containing dissolved S03, which may be withdrawnfor use through pump 22 and pipe 23. Control of conditions within theabsorber tower may be elected in several ways, as by control of thetemperature of the entering liquid S03, and by pressure control electedthrough the agency of valve 2d on SO2 gas vent pipe 25 as a modifier oisystem pressure. Working in this fashion, any desired mixture of liquidsulfur dioxide and dissolved sulfur trioxide can be achieved.

Instead of the fractionator type of absorber shown, other types ofequipment useful for the absorption oi gases in liquids may be used.

Working in another Way, the operation can be utilized for the producingof strong oleum from relatively weaker oleum. Still introducing 20%oleum through pipe ll to the stripper l and denuding it of sulfurtrioxide to produce a denuded 3% oleum, the 20% oleum may be introducedinto absorber I6 through pipe 26 and spray 2l. In this operation, undercontrol of absorber conditions effected in the usual manner by thetemperature of the entering oleum and system pressure as eiected bycontrol of gas vent 2d, any desired strength of oleum can be produced bycontrolled absorption of sulfur trioxide.

It will also be possible, operating in this Way,

for purposes where its use is desirable, as. in

some sulfonation operations, to produce mixtures of oleum and liquidsulfur dioxide.

As an example of the operation, working in tower l at a feed temperatureof 225 F. and a pressure of 2 1b. gauge with a bottom temperature of 250F., a 15% oleum may be lstripped to a 3% oleum. The stripper overheadmay then be treated in absorber i6 at atmospheric pressure and atemperature of .l5-20 F. to produce a liquid consisting of by weight ofsulfur dioxide and 20% by weight of sulfur trioxide. If oleum is used asthe absorption agent, to produce a stronger oleum, the workingtemperature of the absorber will usually be about 40 F. or less, atatmospheric pressure.

Quite obviously. the method may also be used for the strengthening ofsulfuric acid of low concentration, such as for raising theconcentration of a 66 Baum acid by solution of sulfur trioxide therein,and for similar operations.

We claim:

l. That method of handling acidic oxygen products of sulfur comprisingcontacting an oleum containing dissolved sulfur trioxide with gaseoussulfur dioxide under temperature and pressure conditions conducive toevaporation of sulfur trioxide from oleum to produce a gaseous mixtureof sulfur dioxide and trioxide and then in a separate region contactingsaid gaseous mixture with a liquid absorbent for said sulfur trioxideselected from the group consisting of liquid oxides of sulfur andhydrates of sulfuric anhydride to absorb sulfur trioxide therein.

2. The method of claim 1 in which the liquid absorbent used is liquidsulfur dioxide and the product is liquid sulfur dioxide containingdissolved sulfur trioxide.

3. 'I'he method of claim 1 ln which the liquid absorbent used is anoleum and the product is a stronger oleum.

^ FRANK C. FAHNESTOCK.

WILLIAM A. HAGERBAUMER.

